PSI - Issue 64

Uniform

Modal Uniform

Modal Uniform

6

Maria Teresa De Risi et al. / Procedia Structural Integrity 64 (2024) 959–967 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

964

NTC 2018

EC8 2005

ASCE/SEI

1 st DF 1 st JF(T) 1 st JF(C) 1 st SF st st JF(T) st st

JF T BeamSF ColumnSF DF JF C Modal Uniform

X direction Y direction

JF T BeamSF ColumnSF DF JF C Modal Uniform 1 st DF 1 st JF(T) 1 st JF(C) 1 st SF Modal Uniform X direction Y direction 1 st DF 1 st JF(T) 1 st JF(C) 1 st SF Modal Uniform X direction Y direction

Modal Uniform

JF T BeamSF ColumnSF DF JF C Modal Uniform

Modal Uniform Modal Uniform

Modal Uniform

Modal Uniform

SF:

SF:

SF:

SF:

JF T BeamSF ColumnSF DF JF C Modal Uniform Modal Uniform X direction Y direction Modal Uniform

JF T BeamSF ColumnSF DF JF C Modal Uniform Modal Uniform JF T BeamSF ColumnSF DF JF C Modal Uniform JF T BeamSF ColumnSF DF JF C Modal Uniform X direction Y direction Modal Uniform X direction Y direction X direction Y direction JF T BeamSF ColumnSF DF JF C Modal Uniform JF T BeamSF ColumnSF DF JF C Modal Uniform JF T BeamSF ColumnSF DF JF C Modal Uniform X direction Y direction X direction Y direction X direction Y direction

X direction Y direction

JF T BeamSF ColumnSF DF JF C Modal Uniform

JF (T): JF (T):

JF (T):

JF (T):

JF T BeamSF ColumnSF DF JF C Modal Uniform JF T BeamSF ColumnSF DF JF C Modal Uniform

JF T BeamSF ColumnSF DF JF C Modal Uniform JF T BeamSF ColumnSF DF JF C Modal Uniform X direction Y direction X direction Y direction

X direction Y direction

JF (C): JF (C):

JF (C):

JF (C):

X direction Y direction

(a) (b) Fig. 2. Capacity curves up to the first DF with the relevant collapse mechanisms for “modal” distribution : (a) 2-storey and (b) 4-storey building. Failure evolution with S d for (a) 2-storey and (b) 4-storey building. The “ capacity spectrum ”, depending on the specific considered site is then obtained, by using the spectral shape suggested by Italian code (DM 2018), specialized for each of the (about) 6700 municipalities classified as “seismic prone” areas only after 1970, as explained before. Therefore, for each building and each considered municipality a capacity peak ground acceleration (PGA C ) value can be derived (intended as the minimum between the two horizontal directions). In Fig. 3(b), for each building, the median PGA C and the corresponding 16 th and 84 th percentiles are provided depending on the adopted code. This variability around the median value is due to the variability of the spectral shape associated with the construction site (DM 2018) and with the soil conditions (defined as in Mori et al., 2020). For Ns=2, the PGA C according to EC8 2005 and DM 2018 derives from the same kind of failure (i.e., JF(T) in Y direction). On the contrary, for Ns=4, according to EC8 2005, shear failures of beams occur in the X direction even before the first JF(T) failures, providing about the same PGA C of the DM 2018 code. According to the ASCE/SEI code case, the capacity at the SD LS, as in the DM 2018 case, is due to a joint failure (i.e., JF), which however occurs for very higher displacement demands (see Fig. 2), resulting in a higher value of PGA c (especially for Ns=2). 5. Building strengthening and re-assessment Strengthening by solving shear failures without any changes in lateral stiffness is assumed herein as retrofitting strategies. Possible techniques that can be used to this aim are the implementation of FRP wrapping or prestressed steel strips. Herein, FRP wrapping is adopted for beams and columns and prestressed steel strips to solve joint (tensile) failures. Such interventions have been designed for these buildings as shown in De Risi et al. (2023), proving that they